Two new classes of metal-centered probe of protein structure and function in solution are developed and exploited. The first type of probe, applicable principally to calcium binding proteins and to nucleic acids, involves the measurement of environmentally sensitive lanthanide ion fluorescence lifetimes. Measurements on dilute protein solutions for a number of different trivalent lanthanide ions, bound at calcium ion sites, are made possible by the use of a high-power, flash-lamp-pumped, dye laser as an excitation source. The fluorescence lifetime measurements will be used to determine the number of water molecules coordinated to the metal ion. Inter-metal ion nonradiative energy-transfer (lanthanide to transition metal ion and inter-lanthanide) measurements will be exploited as a metal-metal distance probe to gain knowledge about protein structure in solution. The fluorescence emission bands will be examined under high resolution to yield information concerning the details of the metal ion coordination. The fluorescent aromatic aminoacid to lanthanide ion energy transfer step which accounts for the large fluorescence intensity enhancements observed in some systems will be investigated. The techniques developed will be applied to the proteins: thermolysin, parvalbumin, taka amylase, troponin C, and bovine pancreatic deoxyribonuclease A. The second class of probe involves lanthanide porphyrin complexes, which it has been found possible to insert into heme proteins in place of iron protoporphyrin IX. Particular emphasis will be placed on experiments with hybrid hemoglobins (mixed iron-lanthanide species), which retain some degree of biological function.